Process for the production of activated carbon



March 31, 1931. w. M. WILLIAMS 1,798,827

PROCESS FOR THE PRO DUCTT N OF ACTIVATED CARBON Filed Sept. 7, 1928 Patented Mar. 31, 1931 UNITED STATES PATENT OFFICE "WILLIAM MOSES WILLIAMS, OF LONDON, ENGLAND, ASSIGNOR T ACTIVITIES LIMITED,

OF NOTTINGHAM, ENGLAND, A BRITISH COMPANY PROCESS FOR THE PRODUCTION OF ACTIVATED CARBON Application filed September 7,1928, Serial No. 304,593, and in Great Britain September 13, 1927.

The present invention relates to the production of activated carbon, from such carbonaceous material as will evolve combustible gases when heated, such for example as p; bituminous coal, and the term carbonaceous material as hereinafter employed is limited to such material.

According to the invention itis possible to utilize a comparatively cheap carbonaceous n material such as coal dust, in the production of activated or decolourizing carbon, not only as a source of carbon but also as a source of heat in an internal combustion process so that the coal dust in burning may maintain in the necessary temperature and the products of combustion may re-aet with the carbonized coal to produce activated carbon.

It has been found to be possible by properly adjusting the introduction of carbonaceous to material and air to maintain a suiiicient temperature from the combustion of the gases evolved from the said carbonaceous material to bring about activation of the residual carbon by the products of such combustion so that a combustible gas need only be employed for the initial heating of the activation chamber.

The preparation of activated carbon has hitherto been proposed to be effected from carbonized material of vegetable origin such as wood char by suspending particles of the said char in an atmosphere of activating gas, the said particles being kept in motion in the gas by a hot gas blast which latter may be either an activating or an inert gas. Air has been proposed to be employed as an activating gas in this respect at temperatures such as 400 to 600 C.

It has also been proposed to activate carbon by passing activating gases through a carbonaceous material heated in a retort; the

said carbonaceous material being either in the raw state or previously carbonized and in some cases kept in a state of suspension or flotation with a blastof gas. In other cases it was proposed to introduce into the retort air or oxygen so as to burn part of the material with evolution of heat.

According to the present invention actibe vated carbon is produced by a process in which carbonaceous material in powder form (for example bituminous coal) is partially A burnt by injection with a limited quantity of air into a retort at a temperature of substantially 800 C. or over (for example 800 C.-1000 C.) and the partially burnt material is maintained in suspension in the product of its own combustion until activated.

In this way combustible gases are evolved from the carbonaceous material and simul taneously burnt producing gases in situ which at the high temperatures obtained by the intense combustion activate the residual carbon. According to the invention the said gas or vapour or the atmosphere of the combustion chamber may be rendered acid, for example, by introducing acid into the raw material prior to heat treatment. The acid may conveniontly be introduced directly into the combustion chamber. 1

According to the invention the combustion chamber may take the form of an elongated furnace of rounded cross-section and the carbonaceous material is injected thereinto in a tangential direction.

According to the invention the activated material is suddenly cooled or quenched, (for .example, by the introduction of a water spray) at a point in the combustion chamber so situated beyond the combustion zone that the activated carbon may be cooled or quenched as soon as activation is complete.

The apparatus for carrying out the process according to the invention may conveniently comprise a tube or chamber of rounded crosssection either horizontally or vertically arranged and having at one end a nozzle through. which a jet of combustible gas may be introduced under pressure and/or powdered carbonaceous material by means of a current of air under pressure.

The wallofthecombustion chamber are preferably lined with a refractory material capable of promoting surface combustion. Preferably means are also provided to regulate the amount of powdered material introduced by the air stream. The outlet end of the re action chamber may be provided with a steam ejector or similar device by means of which the carbon residues are carried off.

By providing means for varying the supply of air, combustible gas and powder and/or by varying the pressure in the chamber, and also by suitable grading of the carbonaceous material, conditions may be developed within the tube to promote the best results. More intense combustion may be produced by pre-heating the air and also a second blast of air and gas may be introduced into the chamber at any suitable point below the first inlet if the heat obtained by the combustion of carbonaceous material is insufficient to produce the re-. quired temperature for activation.

The accompanying drawing shows in diagrammatic form an arrangement of a combustion furnace suitable for the purpose of the invention.

Referring to the drawing, 10 is a cylindrical-shaped combustion chamber lined with fire bricks 11 and encased in a metal casing 12. At 13 there is an opening directed tangentially to the circular walls of the chamber 10. 14 is a hopper to receive the powdered material which is fed into the tube 18 by means of a screw conveyor 15 which is operated throu h a variable speed gear 16 by a motor 17. y means of a pipe 19, compressed air is introduced to meet the powder as it issues from the pipe 18 and inject it into the combustion chamber. A pipe 20 is also provided for the introduction of a combustible gas. The tube 21 is for the purpose of introducing acid into the combustion chamber from acontainer and the supply is regulated by the cook 22. The activated materials are withdrawn or ejected through the opening 23 and distributed in water contained in a tank 27 by means of a distributing rose 24. A suction pipe 25 is provided for withdrawing the activated material to a filter press or other device not shown for separating it from the water. The residual gases consist largely of carbonic oxide which is allowed to escape through the pipe 26. An opening 28 may also be provided at a point in the combustion chamber so situated that the activated carbon may be cooled or quenched as soon as activation is complete by the introduction of a water spray. The precise position at which such spray should be introduced will depend on the dimensions of the apparatus used and the pressure at which the combustible ingredients are introduced and the relative amounts of air, combustible gas and carbonaceous material forming the jet. It is, however, easy to adjust the position for any given conditions, because a position too near the zone of combustion would give a product insufiiciently activated, whereas a position too far from the combustion zone would not give a good yield.

The following is an example of the process as carried out in an apparatus similar to that just described. Coal dust which had passed through a 200 mesh sieve was introduced into a tube (18) at the rate of oz. per minute,

with cu. ft. per minute of coal gas (the ordinary South London supply) introduced by the pipe (20) into an air blast injected by a pipe (19) into a combustion chamber (10) at the rate of 4 to 4 cubic feet per minute and at a pressure of 23 pounds per square inch. Before introducing the coal dust the apparatus was heated to a bright red heat by the combustion of coal gas (admitted through a pipe 20) and air only. The diameter of the combustion chamber was 3 inches and the length 4 feet. The combustion mixture was injected tangentially and the residual carbon was washed with a diluted solution of sulphuric acid, dried and then retreated by introducing it into the combustion chamber in place of the coal dust as previously described.

It was later found that instead of carbonizing the coal dust in a separate operation and then treating it with acid before the activation process proper the whole process could be conducted in one operation and the acid introduced directl into the combustion chamber, for example, y the pipe 21, the flow being regulated to produce a mere dripping of the acid sufiicient to render the atmosphere of the combustion chamber distinctly acid. Furthermore, when working with a tangential injection of coal dust it was found possible to dispense with the combustible gas as soon as the tube is red hot, because the combustion of the volatile products of the coal with the air introduced gave a suflicient heat to maintain the necessary temperature.

In a further example the apparatus employed was the same as that already described and illustrated in the accompanying drawing except that the diameter of the tube was 12" and the length about 8. The operation was carried out as follows: The reaction chamber was first heated up to a temperature of about 8001000 C. by burning combustible gas introduced by the pipe 20 and air. The combustible gas was then shut off and coal dust ground to 200 mesh was injected with the air in the proportion of about 4 oz. of coal dust to 15 cubic feet of air per minute. Hydrochloric acid was allowed to drip from the tube 21 and the reaction was completed in one operation. Working in this way a residue of carbon was obtained in the bottom of the apparatus in amount about 20% of the coal dust introduced. This residual carbon was found to be highly activated and equal in quality to the best grades of activated or decolorizing carbon.

I claim:

1. Apparatus for the production of activated carbon which consists in a combustion chamber in the form of an elongated furnace of rounded cross section, and means for injecting carbonaceous material thereinto in a tangential direction.

2. In apparatus for activating carbon the combination of an elongated combustion chamber of rounded cross-section, an injector for powdered carbonaceous matter near one end thereof set to deliver the carbonaceous material tanfgentially to the chamber and an extension 0 the chamber at the other end to provide a cooling zone.

3. A process for the production of activated carbon wherein carbonaceous material of the kind described in powdered form is partially burnt by injection with "a limited quantity of air tangentially into a. circular retort heated to a temperature of 800 to 1000 C. so that it is kept in suspension by a whirling movement while passing through the retort, and the path of the material 1n the retort is lengthened.

In testimon whereof I afiix my signature.

' WILL AM MOSES WILLIAMS. 

